You and Your Students!
Vicki Cobb, Education World Science Editor
Sip some cola and an “un-cola” (a lemon-lime soda) without seeing the color. You might be surprised that you can’t tell the difference.
Chemistry, The Senses, Nutrition
Setting the Scene (Background)
Colas and un-colas (for example, Sprite and 7-Up) are all citrus-based drinks.
Most "best guesses" about Coca-Cola's secret formula include one or more of the following ingredients: citric acid, sodium citrate, lemon, orange, and lime.
One obvious difference between colas and un-colas is the color. Cola has caramel color added (which doesn't affect the taste). Would a person who can't see the color of a cola and a clear soda be able to detect the difference? That's what this test is about.
Every cola manufacturer has a formula for its particular brand of cola syrup, and those recipes are very closely guarded secrets. Legend has it that only three people in the world know the recipe for Coca-Cola syrup. I thought you and your students might like to try to mix your own version, so I'm giving you a recipe to play with.
You might want to do Act I as a demonstration. Once students have seen the demonstration, they might want to work in pairs or small groups to verify that it “works.”
Choose a student to help you with this demonstration. Have the student put on a blindfold; secure it in place so you are certain there can be no peeking.
Pour two glasses of soda with ice: One glass should contain a cola, the other an un-cola such as Sprite or 7-Up. Ask your blindfolded volunteer to alternate sips between the drinks. Important: The mouth should be rinsed with water between sips. Switch the glasses around several times, and don't let onlookers give any clues to the sipper. If your subject can tell the difference easily, try it again using the nose clips.
Taste sensitivity diminishes with age. Your students might want to try this at home on their parents and other adults to test out this idea.
Use the ingredients below to mix your own cola:
Try the same blindfolded taste test comparing commercial cola with your homemade version. The blindfold is important, since the two cola versions will look so different.
Behind the Scenes
The taste difference between colas and un-colas is real, although it is much less than most people think. Some of your subjects will be better at telling the difference than others. A nose clip will make telling the difference more of a challenge since smell is an important component to our experience with food and drink. One major difference between these two kinds of soda is sweetness. Which kind is sweeter? (usually the cola).
If some of your students are interested, you can carry the synthetic cola activity further by having them perfect the formula. They should systematically vary the amounts of the ingredients and have a blindfolded friend check each mixture against real cola. For example, keep everything in the same proportion but vary the amount of sugar by half-teaspoonfuls until the homemade soda is a sweet as the commercial brand; then vary the amount of lime juice by half-teaspoonfuls; and so on.
For more information and activities for teaching about fields of force, check out
Sources of Forces: Science Fun with Force Fields
by Vicki Cobb, illustrated by Steve Haefele (The Millbrook Press, 2002).
Article By Vicki Cobb
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